Two novel naturally occurring alpha-methoxy acids from the phospholipids of two Caribbean sponges

The novel (5Z)-2-methoxy-5-hexadecenoic acid (1) was identified in the phospholipids of the sponge Tethya crypta while the also novel acid (6Z)-2-methoxy-6-hexadecenoic acid (2) was found in the phospholipids of the Caribbean sponge Spheciospongia cuspidifera. The methoxy-fatty acids were mainly associated with phosphatidylethanolamine. The double bond positions were determined by gas chromatography/mass spectrometry on the corresponding dimethyl-disulfide adducts and the double bond stereochemistry was ascertained by gas chromatography/Fourier transform infrared spectroscopy. The fatty acid composition of the two sponges is reported.